1. Field of the Invention
This invention relates to a system for controlling the locomotion of a legged robot, and more particularly to a system for quickly stabilizing the attitude of a biped or other legged robot whose attitude has been destabilized owing to an external force, by correcting the footfall position of its free leg.
2. Description of the Prior Art
Biped personal robots are expected to come into common use in the human living environment in the not-too-distant future. In an actual use environment, such robots are apt to bump into people and objects or to be bumped into by people. As such contacts can destabilize the attitude of a biped robot (throw it off balance), there is a high probability of its falling over and becoming incapacitated. A biped robot is particularly susceptible to this problem because its manner of walking by supporting its weight on one leg while moving its free leg forward requires it to stand on one leg for a relatively long time.
Various techniques have been devised for controlling the attitude of biped robots. For example, at The 7th Annual Conference of Robotics Society of Japan, the Waseda University Laboratory proposed a system in which external forces acting on the robot are sensed by a six-dimensional force and torque sensor mounted at the shin portion of each leg link, the change in attitude due to the external forces is determined, and a compensatory action is conducted. In addition Clemson University of the U.S. has proposed a system in which external forces are detected from the angle between the sole of the foot of the supporting leg and the ground, and the change in attitude due to the external force is determined and corrected (IEEE, Transactions on Systems, Man and Cybernetics, Vol. 19, No. 1, 1989).
In both of these prior art systems, the corrective action is taken after determining the change in attitude caused by the external force. The delay between the time when the external force acts on the robot and the time when the action is taken to compensate for the external force is therefore relatively long.